/*
MIT License

Copyright (c) 2019 SergeyBel

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

// the AES library has been modified to reduce heap memory allocation

#include "aes.h"

const unsigned char sbox[16][16] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5,
    0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0,
    0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc,
    0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a,
    0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0,
    0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b,
    0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
    0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5,
    0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17,
    0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88,
    0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c,
    0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9,
    0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6,
    0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e,
    0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94,
    0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68,
    0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

const unsigned char inv_sbox[16][16] = {
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38,
    0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
    0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87,
    0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
    0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d,
    0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
    0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2,
    0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
    0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
    0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda,
    0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
    0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
    0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
    0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02,
    0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
    0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea,
    0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
    0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
    0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
    0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89,
    0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
    0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20,
    0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
    0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31,
    0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
    0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d,
    0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
    0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0,
    0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26,
    0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d, };


AES256::AES256() {}

int AES256::EncryptCBC(const unsigned char* in, unsigned int inLen, const unsigned char* key, const unsigned char* iv, unsigned char* out)
{
    int outLen = GetPaddingLength(inLen);
    memset(out, 0, sizeof(unsigned char) * outLen);

    unsigned char block[16];
    unsigned char roundKeys[240];

    KeyExpansion(key, roundKeys);
    memcpy(block, iv, blockBytesLen);
    for (unsigned int i = 0; i < outLen; i+= blockBytesLen)
    {
        XorBlocks(block, in + i, block, blockBytesLen);
        EncryptBlock(block, out + i, roundKeys);
        memcpy(block, out + i, blockBytesLen);
    }

    return outLen;
}

int AES256::DecryptCBC(const unsigned char* in, unsigned int inLen, const unsigned char* key, const unsigned char* iv, unsigned char* out)
{
    int outLen = GetPaddingLength(inLen);
    memset(out, 0, sizeof(unsigned char) * outLen);

    unsigned char block[16];
    unsigned char roundKeys[240];

    KeyExpansion(key, roundKeys);
    memcpy(block, iv, blockBytesLen);
    for (unsigned int i = 0; i < inLen; i += blockBytesLen)
    {
        DecryptBlock(in + i, out + i, roundKeys);
        XorBlocks(block, out + i, out + i, blockBytesLen);
        memcpy(block, in + i, blockBytesLen);
    }
    
    return outLen;
}

unsigned int AES256::GetPaddingLength(unsigned int len)
{
    unsigned int lengthWithPadding = (len / blockBytesLen);
    if (len % blockBytesLen) {
        lengthWithPadding++;
    }

    lengthWithPadding *= blockBytesLen;

    return lengthWithPadding;
}

void AES256::EncryptBlock(const unsigned char* in, unsigned char out[], unsigned char* roundKeys)
{
    unsigned char *state[4];
	unsigned char mem[16];
    state[0] = mem;
    int i, j, round;
    for (i = 0; i < 4; i++)
    {
        state[i] = state[0] + Nb * i;
    }

    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++)
        {
            state[i][j] = in[i + 4 * j];
        }
    }

    AddRoundKey(state, roundKeys);

    for (round = 1; round <= Nr - 1; round++)
    {
        SubBytes(state);
        ShiftRows(state);
        MixColumns(state);
        AddRoundKey(state, roundKeys + round * 4 * Nb);
    }

    SubBytes(state);
    ShiftRows(state);
    AddRoundKey(state, roundKeys + Nr * 4 * Nb);

    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++)
        {
            out[i + 4 * j] = state[i][j];
        }
    }
}

void AES256::DecryptBlock(const unsigned char* in, unsigned char out[], unsigned char* roundKeys)
{
    unsigned char mem[16];
    unsigned char* state[4];
    state[0] = mem;
    int i, j, round;
    for (i = 0; i < 4; i++)
    {
        state[i] = state[0] + Nb * i;
    }

    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++) {
            state[i][j] = in[i + 4 * j];
        }
    }

    AddRoundKey(state, roundKeys + Nr * 4 * Nb);

    for (round = Nr - 1; round >= 1; round--)
    {
        InvSubBytes(state);
        InvShiftRows(state);
        AddRoundKey(state, roundKeys + round * 4 * Nb);
        InvMixColumns(state);
    }

    InvSubBytes(state);
    InvShiftRows(state);
    AddRoundKey(state, roundKeys);

    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++) {
            out[i + 4 * j] = state[i][j];
        }
    }
}


void AES256::SubBytes(unsigned char** state)
{
    int i, j;
    unsigned char t;
    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++)
        {
            t = state[i][j];
            state[i][j] = sbox[t / 16][t % 16];
        }
    }

}

void AES256::ShiftRow(unsigned char** state, int i, int n)    // shift row i on n positions
{
    unsigned char* tmp = new unsigned char[Nb];
    for (int j = 0; j < Nb; j++) {
        tmp[j] = state[i][(j + n) % Nb];
    }
    memcpy(state[i], tmp, Nb * sizeof(unsigned char));

    delete[] tmp;
}

void AES256::ShiftRows(unsigned char** state)
{
    ShiftRow(state, 1, 1);
    ShiftRow(state, 2, 2);
    ShiftRow(state, 3, 3);
}

unsigned char AES256::xtime(unsigned char b)    // multiply on x
{
    return (b << 1) ^ (((b >> 7) & 1) * 0x1b);
}

/* Implementation taken from https://en.wikipedia.org/wiki/Rijndael_mix_columns#Implementation_example */
void AES256::MixSingleColumn(unsigned char *r) 
{
    unsigned char a[4];
    unsigned char b[4];
    unsigned char c;
    unsigned char h;
    /* The array 'a' is simply a copy of the input array 'r'
    * The array 'b' is each element of the array 'a' multiplied by 2
    * in Rijndael's Galois field
    * a[n] ^ b[n] is element n multiplied by 3 in Rijndael's Galois field */ 
    for(c=0;c<4;c++) 
    {
        a[c] = r[c];
        /* h is 0xff if the high bit of r[c] is set, 0 otherwise */
        h = (unsigned char)((signed char)r[c] >> 7); /* arithmetic right shift, thus shifting in either zeros or ones */
        b[c] = r[c] << 1; /* implicitly removes high bit because b[c] is an 8-bit char, so we xor by 0x1b and not 0x11b in the next line */
        b[c] ^= 0x1B & h; /* Rijndael's Galois field */
    }
    r[0] = b[0] ^ a[3] ^ a[2] ^ b[1] ^ a[1]; /* 2 * a0 + a3 + a2 + 3 * a1 */
    r[1] = b[1] ^ a[0] ^ a[3] ^ b[2] ^ a[2]; /* 2 * a1 + a0 + a3 + 3 * a2 */
    r[2] = b[2] ^ a[1] ^ a[0] ^ b[3] ^ a[3]; /* 2 * a2 + a1 + a0 + 3 * a3 */
    r[3] = b[3] ^ a[2] ^ a[1] ^ b[0] ^ a[0]; /* 2 * a3 + a2 + a1 + 3 * a0 */
}

/* Performs the mix columns step. Theory from: https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_MixColumns_step */
void AES256::MixColumns(unsigned char** state) 
{
    unsigned char temp[4];

    for(int i = 0; i < 4; ++i)
    {
        for(int j = 0; j < 4; ++j)
        {
            temp[j] = state[j][i]; //place the current state column in temp
        }
        MixSingleColumn(temp); //mix it using the wiki implementation
        for(int j = 0; j < 4; ++j)
        {
            state[j][i] = temp[j]; //when the column is mixed, place it back into the state
        }
    }
}

void AES256::AddRoundKey(unsigned char** state, unsigned char* key)
{
    int i, j;
    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++)
        {
            state[i][j] = state[i][j] ^ key[i + 4 * j];
        }
    }
}

void AES256::SubWord(unsigned char* a)
{
    int i;
    for (i = 0; i < 4; i++)
    {
        a[i] = sbox[a[i] / 16][a[i] % 16];
    }
}

void AES256::RotWord(unsigned char* a)
{
    unsigned char c = a[0];
    a[0] = a[1];
    a[1] = a[2];
    a[2] = a[3];
    a[3] = c;
}

void AES256::XorWords(unsigned char* a, unsigned char* b, unsigned char* c)
{
    int i;
    for (i = 0; i < 4; i++)
    {
        c[i] = a[i] ^ b[i];
    }
}

void AES256::Rcon(unsigned char* a, int n)
{
    int i;
    unsigned char c = 1;
    for (i = 0; i < n - 1; i++)
    {
        c = xtime(c);
    }

    a[0] = c;
    a[1] = a[2] = a[3] = 0;
}

void AES256::KeyExpansion(const unsigned char* key, unsigned char w[])
{
    unsigned char temp[4];
    unsigned char rcon[4];

    int i = 0;
    while (i < 4 * Nk)
    {
        w[i] = key[i];
        i++;
    }

    i = 4 * Nk;
    while (i < 4 * Nb * (Nr + 1))
    {
        temp[0] = w[i - 4 + 0];
        temp[1] = w[i - 4 + 1];
        temp[2] = w[i - 4 + 2];
        temp[3] = w[i - 4 + 3];

        if (i / 4 % Nk == 0)
        {
            RotWord(temp);
            SubWord(temp);
            Rcon(rcon, i / (Nk * 4));
            XorWords(temp, rcon, temp);
        }
        else if (Nk > 6 && i / 4 % Nk == 4)
        {
            SubWord(temp);
        }

        w[i + 0] = w[i - 4 * Nk] ^ temp[0];
        w[i + 1] = w[i + 1 - 4 * Nk] ^ temp[1];
        w[i + 2] = w[i + 2 - 4 * Nk] ^ temp[2];
        w[i + 3] = w[i + 3 - 4 * Nk] ^ temp[3];
        i += 4;
    }
}


void AES256::InvSubBytes(unsigned char** state)
{
    int i, j;
    unsigned char t;
    for (i = 0; i < 4; i++)
    {
        for (j = 0; j < Nb; j++)
        {
            t = state[i][j];
            state[i][j] = inv_sbox[t / 16][t % 16];
        }
    }
}


unsigned char AES256::mul_bytes(unsigned char a, unsigned char b) // multiplication a and b in galois field
{
    unsigned char p = 0;
    unsigned char high_bit_mask = 0x80;
    unsigned char high_bit = 0;
    unsigned char modulo = 0x1B; /* x^8 + x^4 + x^3 + x + 1 */


    for (int i = 0; i < 8; i++) {
        if (b & 1) {
            p ^= a;
        }

        high_bit = a & high_bit_mask;
        a <<= 1;
        if (high_bit) {
            a ^= modulo;
        }
        b >>= 1;
    }

    return p;
}


void AES256::InvMixColumns(unsigned char** state)
{
    unsigned char s[4], s1[4];
    int i, j;

    for (j = 0; j < Nb; j++)
    {
        for (i = 0; i < 4; i++)
        {
            s[i] = state[i][j];
        }
        s1[0] = mul_bytes(0x0e, s[0]) ^ mul_bytes(0x0b, s[1]) ^ mul_bytes(0x0d, s[2]) ^ mul_bytes(0x09, s[3]);
        s1[1] = mul_bytes(0x09, s[0]) ^ mul_bytes(0x0e, s[1]) ^ mul_bytes(0x0b, s[2]) ^ mul_bytes(0x0d, s[3]);
        s1[2] = mul_bytes(0x0d, s[0]) ^ mul_bytes(0x09, s[1]) ^ mul_bytes(0x0e, s[2]) ^ mul_bytes(0x0b, s[3]);
        s1[3] = mul_bytes(0x0b, s[0]) ^ mul_bytes(0x0d, s[1]) ^ mul_bytes(0x09, s[2]) ^ mul_bytes(0x0e, s[3]);

        for (i = 0; i < 4; i++)
        {
            state[i][j] = s1[i];
        }
    }
}

void AES256::InvShiftRows(unsigned char** state)
{
    ShiftRow(state, 1, Nb - 1);
    ShiftRow(state, 2, Nb - 2);
    ShiftRow(state, 3, Nb - 3);
}

void AES256::XorBlocks(const unsigned char* a, const unsigned char* b, unsigned char* c, unsigned int len)
{
    for (unsigned int i = 0; i < len; i++)
    {
        c[i] = a[i] ^ b[i];
    }
}

void AES256::printHexArray(unsigned char a[], unsigned int n)
{
    for (unsigned int i = 0; i < n; i++) {
        printf("%02x ", a[i]);
    }
}